The proposed research seeks to determine the steroidogenic capabilities and capacities in vitro of luteal tissue obtained from spotted skunks during the period of delayed implantation and renewed embryonic development and from ferrets on days 6 and 8 of pregnancy. By concentrating on those steroids which are similar in both the skunk and ferret, and in particular those steroids which appear to exhibit the greatest change in relative synthetic rates, I hope to select the luteal compound, which in addition to progesterone, is required to induce implantation in both skunks and ferrets.